Integrated circuits (IC's) are used in a wide variety of commercial electronic products, such as mobile phones, personal digital assistant (PDA's), digital cases, etc. Generally, an IC designed to implement a specific purpose within an electronic device. For example, a mobile phone may comprise an IC for power management, an IC for RF processing, and an IC for multimedia applications. However, an IC designed to implement a specific purpose may contain numerous functions depending on the commercial electronic product in which it is be included. Some mobile phones have peripheral components such as image sensors, MP3 encoders, and LCD displays. In addition there may be different versions or types of peripheral components (e.g., the image sensor may comprise CCD technology or CMOS technology, or there may be different hardware versions or manufacturers of an LCD display). Accordingly, a single IC may need to be compatible with a multitude of different types and versions peripheral components.
In addition to the numerous environments in which a given IC may operate, there are other considerations when manufacturing a commercial electronic product. An IC may contain tens to hundreds of millions of electronic components, such as transistors and capacitors, on a semiconductor substrate. Furthermore, thousands of dies (unpackaged integrated circuits) may be included on a signal semiconductor wafer during the fabrication process. Processing of a wafer is complex, and may consist of numerous steps such as imaging, depositing, doping, etching, planarizing, and cleaning. After wafer processing is completed, the wafer is cut into individual dies, packages, and wired, resulting in the creation of up to tens of thousands of integrated circuits ready to be included in a commercial product. The process of creating an IC is not faultless: many of the dies and/or packaged IC's may contain defects or errors.
In many commercial electronic products, an IC is foxed to a printed circuit board (PCB) along with other electrical, mechanical, or electro-mechanical components. Some integrated circuits are more expensive than the other components. Because the process of fixing the other components to a PCB may cause damage to some temperature sensitive integrated circuits, manufacturers may fix sensitive integrated circuits to the PCB in one of the last manufacturing stages. However, if a defective IC is fixed on a PCB, other components or peripheral devices may be damaged when power is applied. This may render the other components fixed on the PCB, the peripheral components attached to the PCB, or even the PCB itself, valueless. Even if a defective IC does not damage other components or peripheral devices, manufacturing and engineering time and money will be spent testing and repairing the PCB if the IC is defective. Thus, it is desirable to have adequate assurances that any given IC is not defective before it is fixed to a PCB.
There are numerous conventional methods for testing an IC. The wafer may be tested in-between the various processing steps to ensure that it has not been damaged by a previous processing step. Additionally, fabrication houses may perform device testing on the individual dies after wafer processing has been completed. This is to ensure that some of the many devices in the die perform properly. Typically, the cost of this service is charged to the customer. Fabrication houses calculate the percentage of good dies to total dies fabricated in any given fabrication run (the “yield”). Many fabrication houses may also test the die after packaging to ensure that it was not damaged during packaging and to validate the wire bonding process. This service may also be charged to the customer. However, given the number of devices on a typical IC and the numerous environments in which a given IC must operate, the conventional testing processes may be both inadequate and cost prohibitive.
Therefore, a need exists for an apparatus and method to test an integrated circuit that is cost effective and fully exercises substantially all predefined functions of the integrated circuit.